scholarly journals π–π-Induced aggregation and single-crystal fluorescence anisotropy of 5,6,10b-triazaacephenanthrylene

IUCrJ ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 335-347 ◽  
Author(s):  
Katarzyna Ostrowska ◽  
Davide Ceresoli ◽  
Katarzyna Stadnicka ◽  
Marlena Gryl ◽  
Marco Cazzaniga ◽  
...  

The structural origin of absorption and fluorescence anisotropy of the single crystal of the π-conjugated heterocyclic system 5,6,10b-triazaacephenanthrylene, TAAP, is presented in this study. X-ray analysis shows that the crystal framework in the space group P\overline{1} is formed by centrosymmetric dimers of face-to-face mutually oriented TAAP molecules joined by π–π non-covalent interactions. The conformation of the TAAP molecule is stabilized by intramolecular C—H...N(sp 2), N(sp 2)H...π(CN), and C—H...O(sp 2) hydrogen bonds. The presence of weak π–π interactions is confirmed by quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analysis. The analysis of the optical spectra of TAAP in solution and in the solid state does not allow the specification of the aggregation type. DFT calculations for the dimer in the gas phase indicate that the lowest singlet excitation is forbidden by symmetry, suggesting H-type aggregation, even though the overall absorption spectrum is bathochromically shifted as for the J-type. The experimental determination of the permanent dipole moment of a TAAP molecule in 1,4-dioxane solution indicates the presence of the monomer form. The calculated absorption and emission spectra of the crystal in a simple approximation are consistent with the experimentally determined orientation of the absorption and emission transition dipole moments in TAAP single crystals. The electrostatic interaction between monomers with a permanent dipole moment (ca 4 D each) could result in the unusual spectroscopic JH-aggregate behaviour of the TAAP dimer.

2019 ◽  
Vol 21 (19) ◽  
pp. 9740-9746
Author(s):  
Mohammad Babazadeh ◽  
Paul L. Burn ◽  
David M. Huang

Quantum-chemical calculations show that the direction of the transition dipole moment of organometallic phosphorescent emitters is sensitive to molecular geometry.


1990 ◽  
Vol 29 (26) ◽  
pp. 5238-5241 ◽  
Author(s):  
Wolfgang Guentner ◽  
Guenter Gliemann ◽  
Horst Kunkely ◽  
Christian Reber ◽  
Jeffrey I. Zink

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 524
Author(s):  
Austin Biaggne ◽  
William B. Knowlton ◽  
Bernard Yurke ◽  
Jeunghoon Lee ◽  
Lan Li

The aggregation ability and exciton dynamics of dyes are largely affected by properties of the dye monomers. To facilitate aggregation and improve excitonic function, dyes can be engineered with substituents to exhibit optimal key properties, such as hydrophobicity, static dipole moment differences, and transition dipole moments. To determine how electron donating (D) and electron withdrawing (W) substituents impact the solvation, static dipole moments, and transition dipole moments of the pentamethine indocyanine dye Cy5, density functional theory (DFT) and time-dependent (TD-) DFT calculations were performed. The inclusion of substituents had large effects on the solvation energy of Cy5, with pairs of withdrawing substituents (W-W pairs) exhibiting the most negative solvation energies, suggesting dyes with W-W pairs are more soluble than others. With respect to pristine Cy5, the transition dipole moment was relatively unaffected upon substitution while numerous W-W pairs and pairs of donating and withdrawing substituents (D-W pairs) enhanced the static dipole difference. The increase in static dipole difference was correlated with an increase in the magnitude of the sum of the Hammett constants of the substituents on the dye. The results of this study provide insight into how specific substituents affect Cy5 monomers and which pairs can be used to engineer dyes with desired properties.


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